The present invention relates to gas lasers and more particularly to a closed cycle gas laser of the chemical type.
Conventional open cycle continuous wave hydrogen fluoride/deuterium fluoride chemical lasers are typically constrained by several disadvantages that limit their range of applications. Foremost is the inherent safety hazards associated with the toxic exhaust of these systems. Additionally, chemical lasers typically have gas handling problems associated with their fluorine bearing fuels and when operated as an open cycle system inherently have large fuel consumptions which can be very costly when gases such as deuterium are employed. Also the weight and inconvenience of the vacuum exhaust pump and the diffuser system required by most conventional continuous wave chemical laser systems have precluded applications where portability is required.
Freiberg et al in U.S. Pat. No. 4,031,484, filed Nov. 11, 1975 and held with the present application by a common assignee discloses an electrically pulsed hydrogen fluoride/deuterium fluoride chemical laser in which the pulsed chemical laser is operated in a totally self-contained recirculating mode. The laser effluent is chemically scrubbed internally to remove any deleterious ground state hydrogen fluoride. The processed gas which consists of a mixture containing unreacted hydrogen and sulphur hexafluoride as well as sulphur hexafluoride derivatives, is replenished with a small amount of makeup gases, i.e., sulphur hexafluoride and hydrogen which is recirculated into the pulse laser discharge region. Between laser pulses, the hydrogen fluoride molecules which were deactivated during the lasing action are swept out of the cavity and are replaced by a fresh gas mixture.
This technique is adaptable only for the pulse mode of operation. In a continuous wave chemical laser system, molecular hydrogen is mixed and reacted with either a supersonic or subsonic flow of atomic fluorine which has been generated by way of a chemical combustion process, an electrical initiation process, or by thermo means well known in the art. For these continuous wave chemical laser systems it is essential that the two primary reactants, which for the case for the hydrogen fluoride laser is molecular hydrogen and atomic fluorine, be introduced into the laser channel separately and mixed slightly upstream of the optical axis of the resonator. In the hydrogen fluoride continuous wave mixing laser, for example, any molecular hydrogen present in the electrical discharge of the sulphur hexafluoride will react quickly with the atomic fluorine produced by the discharge. As a consequence of the rapid vibrational deactivation rates associated with hydrogen fluoride, the population of the ground state energy level within the gas flow increases rapidly resulting in a very effective but highly undesirable quenching of the hydrogen fluoride laser action within the optical cavity.